Mass dials (scratch dials) are medieval (1100 - 1600) dials found on the south walls of churches. They were usually near the main door or the priest door at about four to five feet above the ground. Due to rebuilding, mass dials can end up almost anywhere on a church, even the north wall. They are frequently found inside a later added porch over the south door.
About 8 or 9 inches across and rather roughly cut, mass dials come in a wide variety of designs, from semi-circles of dots to complete circles with associated radii. Their chronology is difficult to determine but simple versions with only four or five lines are early whilst those with numbers round the edge (rare) are late.
The gnomon, invariably missing, pointed straight out horizontally and so the dial would not record the same hours at all times of the year. The mass dial is in any case usually regarded as an event marker for the church services rather than a time piece.
It should be noted that Saxon Dials form a distinct and separate group of earlier date. They are usually skilfully carved in relief, pre-date mass dials and possibly influence some mass dials but it is difficult to establish a link by either style or geography.
It is thought that the earliest mass dials may be a simple carving of four or five lines from the gnomon hole, possibly with circle or arc later. The Ashton-under-Hill stone also includes an example of ‘four holes in a row’; the row of dots would originally have been horizontal with the gnomon stuck into a mortar line above.
The usual form of later dials has radii principally in the lower half and may be bounded by a circle or an arc of ‘pocks’. Lines above the horizontal are a bit of a mystery in practical terms but were probably ‘space filling’ or alignment lines used if the church was limewashed over. The Alfriston in-lining is modern.
The quality of carving is very variable and some very crudely cut dials are found
There is also an enormous range of sizes recorded, from 70mm diameter to 400mm diameter.
The final phase is probably ‘dials with numbers round the edge’. The numbers can be in the form of some dot arrangement. This latter dial probably represents the end of the mass dial line as the ‘hour line’ spacing seems to be variable rather than a uniform 15º as on many dials. Also there is no ‘mass marker’ at around 9 a.m. which is a feature of many mass dials.
Frequently, several appear on one church but no regional variation in design has been established.